This invention relates to radiators, and, more particularly, to radiators used in spacecraft.
A radiator is designed to radiate heat to its surroundings. Spacecraft whose occupants, electronics, or power sources generate large amounts of heat employ one or more radiators to transfer the generated heat from the interior of the spacecraft to free space and to reflect incident heat from solar radiation exposure. The radiators also aid in dissipating static electricity on the surface of the spacecraft. The radiators are necessary to prevent heating of the interior of the spacecraft to unacceptably high levels. For some spacecraft such as large communications satellites that generate and utilize large amounts of power, removal of excess heat is a significant factor in the design of the spacecraft, and large amounts of radiator surface are required.
In a commonly used construction of a spacecraft radiator, the radiating surface is formed of a large number of individual mirror-like radiators. A single larger mirror-like radiator is not used because of the likelihood that it would crack due to thermal strains. Each mirror-like radiator is 1-2 inches on a side. Each mirror-like radiator is formed of a ceramic-glass substrate about 0.002-0.010 inches thick that is coated on the inwardly facing surface with a metallic silver coating. The metal-coated mirror has a relatively low solar absorptance and a relatively high infrared emittance, so that heat is effectively radiated away without absorbing excessive energy from incident sunlight. The opposite, outwardly facing surface of the ceramic-glass substrate is coated with a layer of transparent indium-tin-oxide that serves to dissipate static charges. The metallic silver-coated inwardly facing surface is bonded to the underlying structure with a silicone adhesive.
This radiator construction is operable and widely used on communications satellites. However, the fabrication of the spacecraft using the individual mirror-like radiators is a time-consuming, expensive process. Hundreds or thousands of individual mirror-like elements are fabricated by deposition processes and then individually attached to the underlying support surface. Because the glass ceramic mirror substrates are thin and large in lateral extent relative to their thickness, they are fragile and easily broken during fabrication, assembly, or service.
There is accordingly a need for an improved approach to the construction of radiators used in spacecraft and for other applications. The present invention fulfills this need, and further provides related advantages.